1. Field of Invention
The present invention relates to a wireless video transceiving technique, especially to a method and an apparatus of wireless video transceiving based on a multi-carrier technique.
2. Description of Prior Art
The conventional video communication generally concerns processes as follows: a video signal is compressed into a video stream, and the video stream is transmitted directly to a wired or wireless communication channel, i.e., via a series of intermediate processes such as source encoding, channel encoding, modulation, channel transmission, demodulation, channel decoding and source decoding etc., so that video transmission and reception are completed. According to the resource allocation method of a current wireless multimedia system (referring to Chinese patent 200510053159.0, with the Publication No. CN1829131), video and voice are transmitted in a sub-carrier allocation manner, but the video transmission is still based on the video stream. However, three different types of frames (I Frame, B Frame and P Frame) and related image header information are contained in the GOP (Group of Picture) of the video stream (referring to FIGS. 1 and 2). FIG. 3 is an coding structure diagram of GOP. As illustrated, the I frame is a start frame to which other frames refer, and the quality of the I frame directly effects the quality of the following frames in the same group. The P frame is a forward predict frame, which is formed by removing similar data with a previous frame based on a comparison with the image of the previous frame. The B frame is a bi-directional frame, which is obtained from a comparison with images of a previous and a next frame. The P frame and the B frame are both dependent on the I frame. Additionally, image header information is also important. The loss of a package containing image header information will directly cause an image associated with this information to not be decoded. In the conventional transmission method based on video stream, the above three types of frames are of different degrees of importance. These figures, and the related image header information, are all actually transmitted in the same manner and under the same channel condition, which is therefore unreasonable. Especially in a wireless channel, certain bit errors will be caused due to factors such as fading and various disturbances etc. If frames are transmitted as described above, once I frame errors occur, or the image header information is lost, the quality of video may be greatly reduced.